Concentration of tin minerals



Patented Aug. 9, 1927.0

UNITED STATES WALTER O. SNELLING, OF ALLENTOWN, PENNSYLVANIA.

CONCENTRATION OF TIN MINERALS Io Drawing.

My invention relates to improvements in the treatment of ores of tin, and more particularly relates to an improved method of concentrating tin ores by superficial alteration of easily reducible tin minerals.

I have discovered that when a tin mineral such as cassiterite, the-principal ore of tin,

is subjected to reducing action, as by electrolytic reduction or the action of nascent hydrogen, the surface of the mineral is partly or wholly reduced tometallic tin, and that the superficially reduced grains or particles may then beseparated from other accompan mg ore minerals or from gangue materia much more completely than by the methods of separation at present known.

As an example of my present invention 1 will describe the method which I ma employ in the treatment ofstream grave containing cassiterite in association with quartz, calcite and like gangue minerals, as well as heavy minerals such as gold, galena and wolframite.

I first separate the lighter gangue minerals by means of tables or jigs, or any of the other customary millingo erations, thus obtaining a concentrate, an I then pass this concentrate over amalgamated plates, to remove gold or other minerals that will be caught on the mercury surface. I then agitate the concentrate with lumps of zinc and dilute hydrochloric acid. After a short period of agitation the surface of all particles of cassiterite will assume a gray, metallic appearance, due to the superficial reduction of the ore particles, and upon again running the concentrate over amalgamated plates, the cassiterite particles may be completely separated from other minerals that may be present, the superficial reduction of the surface of the tin mineral causing these particles to now adhere to the mercury on the plates. In

lhe essential feature of my invention is the superficial reduction of particles of tin ore, and the utilization of the modified surface of the ore particles as a means of separating them from associated materials. In- 'stead of employing amalgamated plates as the means of separation, I may employ flotation or any other suitable form of separation, the chan in the surface of the tin ore as a result 6 reducing action being to so greatly modify the behavior of the ore particles as to make their separation from associated minerals very sharp and complete.

Application filed October 31,, 1925, SerialNo. 66,105.

When employing flotation methods in the treatment of tin ores, I prefer to first subject the properly sized and graded mineral particles to selective flotation, and I then treat the separated material containing the cassiterite by electrolytic reduction or by agitation in zinc drums containing dilute hydrochloric acid, or in wooden drums containing shot zinc and dilute hydrochloric acid, until the surface of the cassiterite particles have been superficially reduced to metallic tin, after .which I again subject the mineral mixture to flotation, by these steps obtaining a very sharp and complete separation.

The reason for themuch more complete separation which I am able to obtain by the methodherein outlined, as compared with any method of separation of tin minerals which has ever been previously described, is to be found in the very wide difference in behavior towards separating operations which is offered by oxide surfaces and metal surfaces. In passing over an amalgamated plate, the oxide ores of tin show no tendency whatever to adhere to the plate, while after superficial reduction the ore particles show very great adhesion to the amalgamated plate, and similarly in flotation the original cassiterite behaves as an oxide in the first flotation operation, and as a metal in the second flotation operation, hus again showing the maximum {possible difference in separating action. M The operation of superficial reduction of the cassiterite particles does not greatly change the specific gravity of the ore mineral, and very slight superficial action, such as may be obtained by electrolytic reduction in from one to two minutes, or bythe action of zinc and hydrochloric acid in from two to five minutes is suflicient to entirely change the behavior of the paritcles of tin ore toward an amalgamated plate or in a flotation cell, and to enable the separation of the particles of tin ore to be made from other particles of heavy minerals that, by reason of similarity in specific gravity or in flotation characteristlcs, can not be separated or can only be separated with great difficulty by other common methods of separation now in use.

The ability to undergo superficial reduction with the formation of a surface film of metal from the action of mild electrolytic reduction or. from the action of nascent hydrogen or from the action of zinc and hydro chloric acid is practically specific to the mineral cassiterite, and accordingly the utilization of this remarkable and quite unique characteristic of the mineral as a means of concentrating the values present in lean ore enables a remarkably clean and sharp separation to be made from other ore minerals.

Although my present invention has been described in connection With its use in the concentration of tin ores, it Will of course be evident that the principle as herein described may be applied to the concentration of the tin oxide dross from the metallurgical treatment of tin, or to the concentration of other fused or semi-fused tin oxide residues, or to tin oxide from any other source, preferably after being compressed, granulated, sintered or fused, to make the material more amenable to physical handling and treatment.

It will be evident that many modifications may be made Without departing from the essential features of the disclosure as herein made, and accordingly no limitations should be imposed in connection With my invention except as indicated in the appended claims.

I claim:

1. In the treatment of minerals, the process which comprises superficially reducing particles of cassiterite electrolytically to metallic tin. and thereafter separating such superficially reduced particles from associated mineral particles.

2. In the treatment of tin ore the process which comprises electrolytically reducing the surface of particles of a tin mineral partially to metallic tin, and thereafter utilizing the modified surface of such particles as a means of separation from other mineral particles.

3. In the concentration of tin ore, the process which comprises subjecting the ore to a process of separation, electrolytically reducing the surface of tin minerals present in the concentrate, and effecting a further concentration by retreating the concentrate by the process of separation previously employed.

4. In the concentration of tin 0res,'the process Which comprises subjecting the ore to flotation treatment, reducing at least a portion of the surface of tin minerals in the concentrate to metallic tin, and again subj ecting the concentrate to a further flotation treatment.

In testimony whereof, I have hereunto subscribed my name this 30th day of October 1925.

WALTER O. SNELLING. 

